The lubricant pump is a mechanical pump which is mechanically driven by the engine. The lubricant pump is fluidically coupled to the combustion engine for pumping a pressurized lubricant to and through the engine.
WO 2012/113437 describes a variable lubricant pump with a pump rotor with radially slidable vanes which rotate inside a shiftable control ring, which is radially shiftable or pivotable with respect to the rotor axis, between a high pumping volume position and a low pumping volume position. The pump comprises a pressure control system to control the discharge pressure of the pressurized lubricant at the pump outlet. The pressure control system comprises a fluidic pressure control chamber to push the shiftable control ring into a high pumping volume direction. The pressure control system also comprises a fluidic pilot chamber to push the control ring into a low pumping volume direction against the forces generated by the pressure control chamber. The pressure control chamber is an antagonist of the pilot chamber. The pilot chamber and the control chamber are directly fluidically connected to the discharge pressure.
The pressure control chamber is also fluidically connected to atmospheric pressure via a pressure control valve which controls the pressure in the pressure control chamber. The pressure control valve is provided with a control valve plunger to open and close a control port of the control valve. The control port of the pressure control valve is connected to an outlet of the pressure control chamber so that the pressure control chamber is connected to atmospheric pressure in the open valve position of the pressure control valve. The pressure control chamber is connected to the discharge pressure in the closed valve position of the pressure control valve. This control arrangement provides short fluidic paths so that the control quality and control stability is high. The discharge pressure of the pump is controlled and kept stable, however, it is the lubricant pressure in or at the engine actually which is the process variable that is relevant and important for a sufficient lubrication of the engine.
DE 10 2008 048 856 A1 describes a similar arrangement with a variable displacement lubricant pump. The pressure control valve is not controlled by the discharge pressure, but is controlled by the engine's lubricant pressure. Practice has shown that a lubricant pump with this control arrangement can cause pressure pulsation and flow rate pulsation. These kinds of pulsations cause performance losses of the lubricant pump and also cause unnecessary wear.